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New laser design promises faster fibre optic broadband

Researchers at Caltech have developed a new semiconductor laser that could transmit data at higher speeds along an optical fibre. The work could pave the way for faster broadband internet and other optical fibre communications.

The new laser design has a much higher spectral purity than the semiconductor distributed-feedback (DFB) laser that is at the heart of today’s fibre optic communications. The new laser has more than 10 times the linewidth improvement compared to commercial semiconductor lasers, the researchers state, with the possibility of further increase in coherence.

The study, led by Dr Christos Santis and carried out in the laboratory of Amnon Yariv, a professor of electrical engineering at Caltech, was published in the online edition of the Proceedings of the National Academy of Sciences.

The new laser design incorporates a high-Q optical resonator as part of the laser cavity, which reduces noise. Some of the noise in commercial semiconductor lasers is due to spontaneous emissions from the semiconductor material, because the photons are both generated and stored in the same material.

In the new design, the stored optical energy is removed by concentrating it in a passive low-loss material and incorporating the high-Q resonator in the laser cavity.

Semiconductor foundry CST Global is leading a UK government-funded project that could substantially reduce the cost of manufacturing high-speed laser diodes for next-generation fibre-to-the-premises (FTTP) networks.

The market for passive optical networks (PON) is expanding rapidly as consumers upgrade their broadband connections to higher speeds. Indeed, this summer, CST Global said it had shipped more than 25 million lasers into PON markets worldwide. To meet the insatiable demand for bandwidth, the next generation of PON lasers will need to be both higher speed and lower cost.